This invention relates to a contact assembly for use in an electrical switching apparatus designed to minimize incorrect assembly.
A conventional electrical switching apparatus in one form typically comprises an electromagnetically actuated device having a magnetic core proximate an armature. Typically, a coil is electrically energized to draw the armature to the magnetic core. The electromagnetically actuated device may be a control relay, a contactor, a motor starter or the like. The armature is operatively associated with a movable device such as an actuator. With an electrical switching apparatus the actuator operates a contact assembly.
A contact assembly may be an integral component of the electrical switching apparatus or it may be an auxiliary device to be added thereto. In either case, the contact assembly typically includes a contact having a pair of stationary contacts and a movable contact. In one known form of a contact assembly, a pusher is movably mounted in an enclosure. The stationary contacts are fixedly mounted in spaced relation with one another. The movable contact is mounted to the pusher. The contact assembly may provide for normally open contact operation or normally closed contact operation. In some conventional contact designs a different geometry stationary contact is used for normally open and normally closed stationary contacts. However, a problem exists in that a simple continuity test may not detect whether the incorrect stationary contacts are installed in such a design. Moreover, the movable contact may include silver contact points on one side of a conductive bar. A simple continuity test will not detect whether the movable contact is facing in the correct direction.
An additional problem of a conventional contact assembly is the improper installation of the pusher. If the pusher moves in a linear direction, and it is mistakenly mounted in an inverted position, then the movable contact will not line up properly with the stationary contacts. Some conventional designs use a small tab on the pusher received in a pocket in the enclosure. However, incorrect assembly may not be obvious during installation until after the cover and housing forming the enclosure are riveted together and the pusher binds during testing. At this point in the manufacturing process the problem is discovered, but the parts may not be salvageable.
Additionally, different variations of contact assemblies may require the availability of multiple pusher designs based on the location and orientation of the movable contacts. For example, both contacts can be normally opened, both contacts can be normally closed, one contact can be normally open and the other normally closed. Additionally, the timing of one contact opening and the other closing can also be altered. These variations necessitate additional parts inventory resulting in loss of economies of scale.
Accordingly, there is a need for a contact assembly for use in an electrical switching apparatus designed to eliminate opportunity of incorrect assembly.
In accordance with the invention there is provided a contact assembly for use in an electrical switching apparatus designed to eliminate opportunity of incorrect assembly.
In accordance with one aspect of the invention there is disclosed a contact assembly for use in an electrical switching apparatus having an actuator. An enclosure comprises an interior space housing first and second stationary contacts fixedly mounted in spaced relation with one another in one of a normally closed position or a normally open position. A pusher is movably mounted in the enclosure and is selectively driven by the actuator to move between a normal position and an actuated position. The pusher comprises a top wall, a bottom wall and first and second side walls connected between the top wall and bottom wall to define an opening having respective first and second ends. First and second longitudinally spaced top ribs are on an inside of the top wall proximate the respective first and second side walls. First and second longitudinally spaced bottom ribs are in an inside of the bottom wall proximate the respective first and second side walls and laterally offset from the respective first and second top ribs. A movable contact is received in the opening. A contact spring is captured between the top rib and the bottom rib at either the first or the second end of the opening to bias the movable contact against the top rib and the bottom rib at the other of the first end and second end of the opening.
It is a feature of the invention that facing surfaces of the first top rib and first bottom rib and the second top rib and second bottom rib are arcuate.
It is another feature of the invention that a portion of each rib at its proximate side wall extends laterally to define a seat for the contact spring.
It is still another feature of the invention that the top ribs are spaced from the bottom ribs to define slots therebetween, whereby the movable contact can be mounted to the pusher by inserting it into the pusher in one of the slots, pressing the movable contact against the contact spring and rotating the movable contact to engage the top rib and the bottom rib at the other of the first end and second end of the opening.
It is a further feature of the invention that the movable contact comprises an elongate bar having contact pads at opposite ends of one face, and a notch on each longitudinal edge of the bar. The notches are longitudinally offset from one another. The pusher top wall and bottom wall have a width that varies in a region where the movable contact is received to coact with the offset notches so the movable contact is installed in a proper orientation. Particularly, the top wall includes offset first and second top notches at first and second longitudinal edges in the region where the movable contact is received and wherein the bottom wall includes offset first and second bottom notches at its first and second longitudinal edges in the region where the movable contact is received. The first top notch is offset from the first bottom notch and the second top notch is offset from the second bottom notch.
It is yet another feature of the invention that the first and second stationary contacts are of a first configuration for normally closed operation and a second configuration for normally open operation. The configurations are selected so that the movable contact does not contact the stationary contact if an incorrect configuration is fixedly mounted in the enclosure.
It is still another feature of the invention that the pusher comprises a neck extending through an opening in the enclosure for engagement with the actuator and the enclosure comprises an asymmetric rib on one side of the opening and the pusher comprises an asymmetric notch in the top wall on one side of the neck receiving the rib to prevent incorrect assembly of the pusher in the enclosure.
There is disclosed in accordance with another aspect of the invention a contact assembly for use in an electrical switching apparatus having an actuator. The contact assembly comprises an enclosure comprising an interior space housing first and second stationary contacts fixedly mounted in spaced relation with one another in one of a normally closed position or a normally open position. A pusher is movably mounted in the enclosure and is selectively driven by the actuator to move between a normal position and an actuated position. The pusher comprises a top wall, a bottom wall and first and second side walls connected between the top wall and bottom wall to define an opening having respective first and second ends. A first pair of ribs at the opening first ends defines a first slot therebetween. A second pair of ribs at the opening second end defines a second slot therebetween. The slots, in cross section, are partially circular. A movable contact is received in the opening. A contact spring is captured in the first slot or the second slot to bias the movable contact against the respective second pair or the first pair of ribs.
There is disclosed in accordance with yet another aspect of the invention the method of assembling a contact assembly for use in an electrical switching apparatus having an actuator. The method comprises providing an enclosure comprising an interior space housing first and second stationary contacts fixedly mounted in spaced relation with one another in one of a normally closed position or a normally open position. A pusher is provided comprising a top wall, a bottom wall and first and second side walls connected between a top wall and a bottom wall defining an opening having respective first and second ends. A first pair of ribs at the opening first end define a first slot therebetween. A second pair of ribs at the opening second end define a second slot therebetween. The slots, in cross section, are partially circular. A contact spring is inserted in the first slot or the second slot to be captured by the respective first pair of ribs or the second pair of ribs. A movable contact is inserted in the pusher by inserting the movable contact in the other of the first and second slots, pressing the movable contact against the contact spring and rotating the movable contact to engage the respective first or second pair of ribs. The pusher is inserted in the enclosure for selective movement by the actuator to move between a normal position and an actuated position to selectively make or break electrical contact between the movable contact and the stationary contacts.
Further features and advantages of the invention will be readily apparent from the specification and from the drawings.